In the loading and off-loading of trucks, more specifically, tractor-trailor trucks, it is desirable to seal the area between terminal dock and/or shelter against inclement weather. At the same time, it is important to provide such combined dock seal and shelter as will be able to withstand substantial abuse, as for example: getting hit by pallets and forklifts. Also, from the outside, the dock and/or shelter gets abused by everything from rough weather to sharp gadgets and projections rendering the dock seal and shelter exposed to extraordinary wear and tear. Accordingly, the present invention is adapted to provide at a given warehouse or building dock, a protective unit that provides a weather-tight seal when compressed by trailer or truck, wherein its rear doors are open and folded back along the sides of the truck and/or trailer. It is desirable that such a dock shelter not only permit complete and unobstructed trailer access, but also provide outstanding weather protection, the shelter being mounted along the outer perimeter of the door opening of the warehouse or terminal building. It is imperative that such a shelter permit free access, while a side curtain assembly for trailer hinge gap closure is closed upon the sides during truck/trailer entry; likewise the vehicle should be sealable by head curtain within the shelter. More specifically, the invention is a hinge gap closure unit which may be retrofitted to existing storage shelters in truck/trailer loading and off-loading. The unit is sufficiently versatile to accommodate a truck trailer which is out of position relative to a dock center as defined by the building construction. The dock center is determined by bumpers and dock sills which are operatively disposed, adjacent the door opening of the building.